The long-term objective of our research is to understand the neural basis for the normal and abnormal development of visual functions in primates. In particular this proposal focuses on the effects of normal and abnormal visual experience on long-range interactions in cortical neurons. The ability to perceptually integrate local features over distance (e.g., contour integration) does not emerge until relatively late after birth and early onset strabismus, if untreated, severely disrupts the normal development of contour integration and feature binding. The neural basis of the subnormal perceptual binding in normal infants and strabismic subjects is not well understood. In adult monkeys cortical neurons are capable of integrating signals over a large area that surrounds their "classic receptive fields" (CRFs), and this ability to integrate over distance is thought to be important for perceptual feature integration and binding. However, we know very little about the postnatal development of the cortical circuitry underlying these long-range interactions in individual neurons, mainly because the stimuli employed in nearly all previous developmental studies, including ours, simultaneously activated the CRFs and the surrounds of cortical neurons. Therefore, in the proposed experiments, we will employ microelectrode recording methods in anesthetized and paralyzed monkeys to investigate the normal and abnormal development of the cortical circuitry that mediates long-range integration in rhesus monkeys (Macaca mulatta). The proposed experiments focus on two major issues: 1) what is the status of long-range signal interactions in cortical areas V1 and V2 in neonates and how does the nature and degree of the interaction change during maturation and 2) how does discordant binocular vision early in life alter this long-range cortical processing. Many of the proposed experiments are designed to test new hypotheses that have been formulated based on the data obtained in our previous studies. The proposed research will provide a better understanding of how cortical neurons integrate excitatory and inhibitory signals during early development and how binocularly conflicting signals early in life may alter the maturation of the underlying cortical circuitry. The results will hopefully have an impact on the development of effective strategies for the prevention and treatment of vision disorders.